synthetic rigging and UV impact

[Mark Johnson]

Originally Posted by jfranta

We have done, and continue to do UV testing on Dynex Dux (Heat Stretched/ Work Hardened Dyneema). Since we use and promote this for standing rigging this is very important to us. Dyneema fibers are the best synthetic fibers for UV resistance. We have enough data to recommend a 5-8 year replacement interval in the tropics. The data is still coming in and I believe that we will end up recommending an 8 year replacement interval for standing rigging. All this is for uncovered Dynex Dux that is/was initially treated with a Urethane Coating to help with friction and UV resistance.
Keep in mind that most steel manufacturers recommend an 8 year replacement interval for salt water boats.

The mechanism for UV damage on dyneema is such that the line experiences some external UV damage and then becomes somewhat opague for UV Rays so the damage rate diminishes considerably.

Also, this is based on the fact that we size the line for Stretch and Creep (not breaking strength). This type of sizing always ends up with line that is 2-5 times stronger than 1x19 spec'd for the same application. So you have a considerable factor of safety for strength.

John Franta, Colligo Marine

Hi John,
The comparison that I would like to see between Dux and 316 SS wire, is @ 18 or 20 years old. Of the countless thousands of boats in our area, (Eastern NC), there has only been one dismasting in the last 5 years to my knowledge, and it was a new racing boat under extreem conditions. If one removes from the conversation the < 5% who are cruising all over the world, or live full time in the tropics... The other 95% spend winters in the Bahamas, are daysailors & local cruisers, or make a couple of one or two year Caribbean cruises... still spending the majority of their years in our moderate lattitudes, and brackish water. Of this 95% of cruisers around here, almost all go over 18 or 20 years before changing out their rigging, some even go to 30 years, (admittedly at their own risk)! Has your accelerated UV testing made a compairison to wire at this 18 + year life span, under the above circumstances?

Another point I am curious about... You made up a couple of DUX runners for me that came out GREAT. Thanks for the accuracy! They are for my running backstays, and DUX seems like a perfect application here. I normally leave them "made up" and fairly snug, to use as a handhold when boarding the boat. When using the staysail, I will put 4 more turns on the "quick adjust" handle turnbuckles, but so far, haven't given them the acid test.
I go to the boat daily, and have noticed that @ 75 degrees F, the runners are quite snug, but @ 40 degrees F, perhaps that same morning, they hang completely limp. Since solid materials expand when heated, and contract when cooled, it can't be that the DUX has gotten longer on a cool morning. I assume that the metal mast has contracted at a rate vastly higher than the DUX, creating loose runners in the morning. Presumably with wooden or composite spars this is less of a problem,. My wire rigging has never done this "changing tune with temperature", and I imagine that it's because the wire expands and contracts at a rate somewhat similar to the metal mast.

With aluminum mast that are long & skinny, (like mine), and dependant on consistant shroud tension to keep the mast in column, wouldn't this become a problem if I tune the rig in the summer, then go sailing on a cool fall day? Has anyone else noticed this characteristic? I have done a LOT of reading on synthetics, and have yet to see this subject brought up...

Best regards, Mark

[Quester51]

This question is for John Franta,
In researching Dynex Dux I have read where some users felt that the UV opaqueness could be rubbed or chafed off by halyards, lines, sheets etc. What has been your experience with this possible problem?
Thanks,
Tony